Thursday, April 7, 2011

Holograms in True Color - ScienceNOW

Holograms in True Color - ScienceNOW: Now, researchers report today in Science that they can create true-color holograms that can be viewed using only white light. Like the first holograms, the new technique uses lasers to generate an interference pattern, says Satoshi Kawata, a photonics physicist at Osaka University in Japan. To capture colors, Kawata and his colleagues illuminate the original object with three different lasers: red, blue, and green, the three primary colors of projected light. They store the hologram in a light-sensitive material coated with a thin layer of metal such as gold or silver, a veneer that contains free electrons that are easily excited when struck by radiation such as light waves.

To reproduce a 3D image, the researchers bathe the metal-sheathed material in ordinary white light, which contains all wavelengths of visible light (including red, blue, and green). That white light excites the free electrons; their resulting movements and oscillations (so-called surface plasmons) in turn give off light that regenerates the image

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